Programs

Python Program for Reverse String

Python is a high-level, multi-functional programming language – among the most powerful and versatile of our times. 

Its language constructs and object-oriented design philosophy facilitates logical, clear, and concise coding and supports various programming paradigms for projects of any scale and magnitude. 

It lays particular stress on the simplicity and readability of code and consists of several compact modular libraries with inbuilt functionalities for virtually all types of specialized operations. 

What are Strings 

Strings are arrays of data in the form of continuous sequences of Unicode characters. They may include alpha-numerical characters, special characters, and spaces. In Python, a string is typically found within single or double quotation marks. Square brackets may be used to access characters within a string.

Python Strings

The Python string library consists of a vast range of inbuilt operations that may be used to manipulate, modify and reformat strings in a variety of ways. But it does not include an inbuilt ‘reverse( )’ operation, which is no surprise, really, given that the string reversal operation is rarely used in routine coding. 

There are, however, multiple methodologies by which one may reverse a string on Python. These are important to know, given that this is an oft-asked question that Python programming candidates may encounter in interviews.

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Different ways to reverse a string in Python

  1. Using the Iterative approach
    1. The ‘for loop’ method
    2. The ‘while loop method
  2. Using the recursive approach 
  3. Using the stack approach
  4. Using the extended slice syntax approach
  5. Using the join ( ) and reversed( ) approach

1. Using the iterative approach:

  • The ‘for loop’ method

In this method, the code summons a function to reverse a string that iterates to each element, intelligently joining each character at the start in order to arrive at a perfectly reversed string. 

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  • The ‘while loop’ method:

A variation on the ‘for loop’ method, the ‘while loop’ is initialized after the str variable is assigned a particular string value. And at each iteration, the value corresponds inversely to the original string count to return a precisely reversed string.

  • Using the recursive approach:

In the recursive method, the string is passed through a recursive operation to arrive at a reversed string. The function is conditional to the string length. 

If string length equals zero, the string is immediately returned unaffected. If not, the reverse function kicks in recursively to slice each element of the string except the initial character, which is summarily assigned to the end of the sliced string to return a perfectly accurate reversed string.

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  • Using the stack approach:

The stack method begins with the creation of an empty stack. Each element of the string is fed into the stack one at a time. Then, each character in the stack is popped individually and put back into the string to emerge in a precisely reversed sequence.

  • Using the extended slice syntax approach:

The extended slice syntax method provides a [start,stop,step] field. Providing no start and stop fields values denotes default to 0 string length, while a step field value of “-1” effectively returns a precisely reversed string.

  • Using the join( ) and reversed( ) approach:

In the join( ) and reversed( ) method, the reversed( ) functionality yields a reversed iterator for any given string. When combined with the join( ) functionality, all the characters in the string merge into a continuous string in a reversed sequence.

Uses of reversing a string in Python:

  1. String reverse is used for debugging the code or as an alternate way of writing a loop.
  2. It is also used to check whether a given string is a palindrome or not.

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